Sound Intensity - Sound Intensity Level

Sound intensity level or acoustic intensity level is a logarithmic measure of the sound intensity (measured in W/m2), in comparison to a reference level.

The measure of a ratio of two sound intensities is

$L_\mathrm{I}=10\, \log_{10}\left(\frac{I_1}{I_0}\right)\ \mathrm{dB} \,$

where I₁ and I₀ are the intensities.

The sound intensity level is given the letter "L_I" and is measured in "dB". The decibel is a dimensionless quantity.

If I₀ is the standard reference sound intensity

$I_0 = \;10^{-12} \, \mathrm{W/{m}^{2}} \,$

(W = watt), then instead of "dB SPL" we use "dB SIL". (SIL = sound intensity level).

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—Robert Frost (1874–1963)

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—George Bernard Shaw (1856–1950)

“No man loses ever on a lower level by magnanimity on a higher.”
—Henry David Thoreau (1817–1862)